Internet of Things (IoT) have wide ranges of applications. One of interesting application is for detection and monitoring ship mobility in harbor. Monitoring the ship in harbor may not need a large monitoring system such as satellite and radar because of limited area. In this paper, we propose a ship detection using IoT. We use four sensors to observe ship-generated waves and combine them using our proposed formula to detect location of the ship real time. We measure radius detection as the average distance from point of interest. We conduct experiments based on two variables, i.e.: sensor distance and ship speed. We show that as the sensor distance increases, the radius detection increases. Moreover, as the ship speed increases, the radius detection decreases. The increasing of sensor distance causes decreasing the amplitude of ship-generated waves. Otherwise, the increasing ship speed improves amplitude of the ship-generated waves. We can see that radius detection is 0.5 m when ship speed is 3 m/s.